It is well known that the use of leukocyte-poor blood will lessen the incidence and severity of febrile non-hemolytic transfusion reactions in sensitized patients. Methods to prepare leukocyte- poor red cells, however, involve entering the sterile blood unit, with consequent 24-hour outdating of the unit, or the use of expensive microaggregate filters at the time of transfusion. A blood storage system has been developed that permits removal of donor leukocytes shortly after donation by means of an integral inline cellulose acetate filter. This system employs a citrate- phosphate-dextrose-adenine-one (CPDA-1) anticoagulant/ preservative solution and dextrose/adenine additive solution which permits 49-day red cell storage. This study is designed to evaluate the in vivo survival of the red cells stored in this system. This information must be obtained before the system can be considered for licensure. Units will be drawn from normal adult, non-pregnant volunteers, filtered and stored for 49 days. A 1-2 ml aliquot of red cells labeled with 51 chromium will be reinfused into the original donor and the in vivo survival measured. Autologous 99m technetium labeled red cells will be simultaneously injected to measure red cell volume.